Re: "Age of the Cybersaur" - Tail whipping

["Allan Edels" <edels@email.msn.com>]

Nathan:

    Thanks for clarifying my earlier post with more detail.  BTW, I had
heard about the towel snap being supersonic nearly 20 years ago - nice that
someone has documented it.

    I wonder if you missed an earlier discussion on whether sauropods ever
laid down on their sides.  Someone suggested the image of a horse trying to
get up after lying on its side.  They rock their bodies back and forth and
nearly snap their bodies to an upright position.  Based on that, I wondered
if the long tails and long necks of the sauropods might have been used in
similiar fashion.  I also suggested that maybe you could run your tail-whip
simulation in reverse (sort-of) to see if the tails could generate enough
power to lift a lying sauropod off its side.  (Essentially postulating two
uses for sauropod tails - 1) sound generation, & 2) supplying enough
momentum to bring a sauropod to a standing position from a lying position).
What do you think?

BTW:
    For those of you who missed Nathan's demonstration with his whip at the
DinoFest Symposium, it was certainly one of the more entertaining and
enlightening talks.  As a city-boy, I haven't been around whips too much,
and the harmonics that the whip produces does not come through on TV or
Movies.  (It also echoed really nicely in the room used for the talk).

    Allan Edels


-----Original Message-----
From: Nathan Myhrvold <nathanm@MICROSOFT.com>
To: 'edels@email.msn.com' <edels@email.msn.com>; dinosaur@usc.edu
<dinosaur@usc.edu>
Date: Saturday, September 05, 1998 3:04 AM
Subject: RE: "Age of the Cybersaur" - Tail whipping


>Bullwhips crack because of a sonic boom, or shock wave caused by the tip of
>the whip exceeding the speed of sound.   This has been documented since the
>late 1950s when photographic techniques became good enough to capture the
>tip of the whip.   Most whips measured achieve about Mach 2 - twice the
>speed of sound.
>
>I recently found the following student project on the net - it documents
>that snapping a towel (as often occurs in locker rooms) is actually
>supersonic as well.
>
>http://www.pacsci.org/public/education/gallery/high_speed_photos/towel.html
>
>It is only a little over Mach 1, so the sound is not as sharp as a Mach 2
>bullwhip, but the principle is the same.
>
>Our research (done with Phil Currie) showed that it is physically feasible
>that the diplodocid sauropods used their tails like bullwhips, with the
tips
>going faster than sound.   This was possible without putting unusual
>stresses on the tail, and without requiring unusual amounts of energy.  We
>have a strong but circumstantial case that it is biomechanically possible,
>but since a behavior does not fossilize directly one can't actually prove
>that the diplodocids did this.
>
>Nathan
>
>